Table 3.3  The peak fluorescein values as measure with the fluorophotometer following­ topical application of fluorescein to the treated eye

topical applications of fluorescein. The experiment supports the difficulty of delivering­ fluorescein to the posterior segment of the eye with topical corneal applications.

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Chapter 4

Systemic Route for Retinal Drug Delivery: Role of the Blood-Retinal Barrier

Masanori Tachikawa, Vadivel Ganapathy, and Ken-ichi Hosoya

Abstract  Systemic delivery of therapeutic drugs to the retina is hindered by the presence of the blood-retinal barrier (BRB) which consists of retinal vascular endothelial cells (inner BRB) and retinal pigment epithelial cells (outer BRB). Recent progress in the BRB research has revealed that the BRB expresses a wide variety of transporters essential for the blood-to-retinal influx transport of nutrients and their analogs. At the same time, the BRB also possesses several transporters responsible for the retina-to-blood efflux transport of xenobiotics and drugs, thus being involved in the removal of potentially harmful compounds from the retina. This information can be exploited to our advantage to establish efficient strategies for optimal delivery of clinically relevant therapeutic drugs into the retina.